I have large orange stems with brown slimy tops growing up through my mulch.
Fungus. This is not unusual in mulch, particularly wood mulch. Wet weather can bring it on. Try stirring it up with a rake to inject some air around the fungus. Use mulch that is less prone to fungus such as cocoa hulls or licorice root. Fungus population rises and falls as the wood breaks down, so a really bad year is often followed by a better one.